I'd like to know how late in the day tournament play is going to happen. From the schedule on http://2011amworlds.com/?l=t&pageStewardLink=7036, it looks like it ends every day at 3:00 but I'm a little confused by it. If I head to Chili at 4:00 tomorrow, will there still be match play going on?

When looking at the schedule, you need to realize that there is no "End Time.". The Tee Times are on the schedule, and you can imagine that it is going to take a few hours to finish a round, especially at 3:00 in the heat. If you arrive at a course at 4:00, there will absolutely be tournament play taking place if there was a 3:00 tee time.